1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a liquid crystal display (LCD) device to improve the resolution for a white color and a method for fabricating the same.
2. Discussion of the Related Art
Demands for various display devices have increased with the development of an information-based society. Accordingly, many efforts have been made to research and develop various flat display devices such as liquid crystal display (LCD), plasma display panel (PDP), electroluminescent display (ELD), and vacuum fluorescent display (VFD). Some species of flat display devices have already been applied to displays for various equipment.
Among the various flat display devices, liquid crystal display (LCD) devices have been most widely used due to advantageous characteristics of thin profile, lightness in weight, and low power consumption. In addition to mobile type displays, LCD devices have been developed for computer monitors and televisions to receive and display broadcasts.
The LCD device includes first and second substrates bonded to each other at a predetermined interval, and a liquid crystal layer formed between the first and second substrates. The first substrate (TFT array substrate) includes a plurality of gate lines arranged along a first direction at fixed intervals, a plurality of data lines arranged along a second direction perpendicular to the first direction at fixed intervals, a plurality of pixel electrodes arranged in a matrix-type configuration within pixel regions defined by crossings of the gate and data lines, and a plurality of thin film transistors for transmitting signals from the data lines to the pixel electrodes. The second substrate (color filter array substrate) includes a black matrix layer that prevents light from leaking on portions of the first substrate except the pixel regions, an R/G/B color filter layer for displaying various colors, and a common electrode for producing the image. The first and second substrates are bonded together by a sealant, and liquid crystal is injected between the first and second substrates. Alignment layers are respectively formed on opposing surfaces of the first and second substrates, wherein the alignment layers are rubbed to align the liquid crystal layer.
Herein, the color filter layer of the second substrate is comprised of unit pixels including three sub-pixels, wherein the three sub-pixels are formed of R (red), G (green), and B (blue) colors. Recently, to improve luminance of the image displayed on the LCD panel, the unit pixel may include four sub-pixels. That is, in addition to the sub-pixels of R, G, and B colors, a sub-pixel of a white (W) color may be included, so that the unit pixel may be comprised of the sub-pixels of R, G, B, and W colors.
A related art color filter substrate using a color filter layer of R, G, B, and W will be described with reference to the accompanying drawings.
FIG. 1 is a schematic view of a related art color filter substrate. FIG. 2 is a cross sectional view of a related art color filter substrate along I-I′ of FIG. 1.
As shown in FIG. 11 and FIG. 2, a related art color filter substrate includes a substrate 10, a black matrix layer BM, first to fourth color filter layers 11a, 11b, 11c, 11d, and an overcoat layer 12. First to fourth pixel regions are repetitively formed on the substrate 10, and the black matrix layer BM is formed on an entire surface of the substrate 10, except the pixel regions, to prevent light leakage on the portions other than the pixel regions. Also, the first, second, third, and fourth color filter layers 11a, 11b, 11c, 11d are formed on the respective pixel regions, and the overcoat layer 12 is formed on the entire surface of the substrate 10 including the respective color filter layers 11a, 11b, 11c, 11d. 
Herein, the first, second, and third color filter layers 11a, 11b, 11c are formed of dyed resist or resin. That is, the first, second, and third color filter layers 11a, 11b, 11c are respectively formed of red-dyed, green-dyed, and blue-dyed resist or resin to display the respective colors. The fourth color filter layer 11d is formed of transparent resist or resin having no pigment to improve luminance by transmitting the incident light.
A method for fabricating the related art color filter substrate will be described as follows.
FIG. 3A to FIG. 3C are cross sectional views of the fabrication process of a related art color filter substrate along I-I′ of FIG. 1.
First, as shown in FIG. 3A, after preparing the substrate 10 having the first to fourth pixel regions repetitively arranged, chrome or resin is deposited on the substrate 10, and then is patterned by photolithography. As a result, the black matrix layer BM is formed on the entire surface of the substrate 10 including the respective pixel regions.
Subsequently, as shown in FIG. 3B, the red resist or resin is coated on the substrate 10 having the black matrix layer BM, and then the substrate 10 coated with the red resist or resin is patterned by photolithography, thereby forming the first color filter layer 11a on the first pixel region of the substrate 10.
Next, as shown in FIG. 3C, the green resist or resin is coated on the substrate 10 having the first color filter layer 11a, and then the substrate 10 is patterned by photolithography, thereby forming the second color filter layer 11b on the second pixel region of the substrate 10.
After that, the blue resist or resin is coated on the substrate 10 having the first and second color filter layers 11a, 11b, and then the substrate 10 is patterned by photolithography, thereby forming the third color filter layer 11c on the third pixel region of the substrate 10.
Subsequently, the transparent resist is coated on the substrate 10 having the first, second, and third color filter layers 11a, 11b, 11c, and then the substrate 10 coated with the transparent resist is patterned by photolithography, thereby forming the fourth color filter layer 11d on the fourth pixel region of the substrate 10.
Then, the overcoat layer 12 is formed on the entire surface of the substrate 10 including the first, second, third, and fourth color filter layers 11a, 11b, 11c, 11d, thereby completing the fabrication process of the color filter substrate.
However, the related art color filter substrate using the R, G, B, and W color filter layers has the following disadvantages.
In the related art fabrication process of the color filter substrate, in order to form the white color filter layer, it requires additional process steps of coating the transparent resist on the substrate, and etching the substrate coated with the transparent resist by photolithography, thereby increasing the fabrication time, and decreasing the yield.
Also, there is a difference of resolution between the white color obtained by the white color filter layer of the color filter substrate, and the white color obtained by the R, G, and B color filter layers of the other pixel regions, thereby deteriorating the entire color resolution for the white color.